The semiconductor integrated circuit (IC) industry has experienced rapid growth. As the dimensions of transistors decrease, the thickness of the gate oxide must be reduced to maintain performance with the decreased gate length. However, in order to reduce gate leakage, high dielectric constant (high-k) gate insulator layers are used which allow greater physical thicknesses while maintaining the same effective thickness as would be provided by a typical gate oxide used in larger technology nodes.
Additionally, as technology nodes shrink, in some IC designs, there has been a desire to replace the typically polysilicon gate electrode with a metal gate (MG) electrode to improve device performance with the decreased feature sizes. One process of forming the MG electrode is termed “gate last” process in which the final metal gate electrode is fabricated “last” which allows for reduced number of subsequent processes, including high temperature processing, that must be performed after formation of the gate.
However, problems arise when integrating a high-k/metal gate feature in a CMOS technology process flow due to various factors such as incompatibility of materials, complex processes, and thermal budgets. Therefore, for these advances to be realized, similar developments in IC processing and manufacturing are needed.
Like reference symbols in the various drawings indicate like elements.